The purpose of this blog is to provide a brief resume of
the types of spectacle lenses available to the patient
for better vision (visual needs).
Here we can discuss and share all about ophthalmic lenses, theories, individual findings, inventions, optical standards, tolerance, errors, complex optics and more..

People of all ages require regular eye examinations to check vision and eye health. This chart provides a quick test to see how your reading and distance vision compares to what is expected in 'normal vision'.

HOW TO DO THESE TESTS

Test one eye at a time.
(Cover one eye but keep both eyes open.)

Wear glasses or contact lenses, if usually worn.
(If you use separate reading glasses, wear them for the reading vision test only.)

Do the tests in a well-lit area.
(Avoid shadows on the chart.)

Do not squint, relax your eyes.

READING VISION TEST

Especially useful for people 40 years or older.

Cover one eye ata time and hold this card at your normal reading distance (about 40 cm from your eyes.)

Can you read the bottom line on the chart below?

Distance Vision Test

Carry out the two tests below at 1.5m
(ex. Place card on floor and tilt head down.)

MYOPIA

Can you read ALL the black and grey letters with each eye?

ASTIGMATISM

Do any of these lines appear much darker than others with each eye?

How Did you Perform

If you marked any of the RED boxes, keep this card and visit your eye care practitioner who will further assess your vision.

Learn how to transpose an eyeglass prescription easily by learning a few simple rules!

Transposing a prescription is one of the most common actions when working in an optical laboratory, doctor’s office or even on a retail floor when an optician. Some eye doctors prescribe eyeglasses in what is called plus cylinder, and others do so in minus cylinder. Regardless of which is used, the prescriptions are the same. This can be proven by transposing the eyewear prescription.

Transpose a prescription written in plus cylinder form to minus cylinder form as follows:

1. Add the sphere and cylinder powers to determine the new sphere power.
2. Change the sign of the cylinder.
3. Change the axis by 90 degrees.

Example 1:

Transpose -3.00 +2.00 x 30

Step 1

Add the sphere and cylinder powers to determine the new sphere power.

(-3.00) + (+2.00) = -1.00

Step 2

Change the sign of the cylinder

-2.00

Step 3

Change the axis by 90 degrees. (if the axis is 90 or less than 90, add 90 degrees to the axis, if the axis is greater than 90 deduct 90 from the axis)

120

The transposed prescription is: -1.00 -2.00 x 120

Example 2:

Transpose -3.00 -2.00 x 30

Step 1

Add the sphere and cylinder powers to determine the new sphere power.

(-3.00) + (-2.00) = -5.00

Step 2

Change the sign of the cylinder

+2.00

Step 3

Change the axis by 90 degrees. (if the axis is 90 or less than 90, add 90 degrees to the axis, if the axis is greater than 90 deduct 90 from the axis)

120

The transposed prescription is: -5.00 +2.00 x 120

Example 3:

Transpose +3.00 -2.00 x 30

Step 1

Add the sphere and cylinder powers to determine the new sphere power.

(+3.00) + (-2.00) = +1.00

Step 2

Change the sign of the cylinder

+2.00

Step 3

Change the axis by 90 degrees. (if the axis is 90 or less than 90, add 90 degrees to the axis, if the axis is greater than 90 deduct 90 from the axis)

120

The transposed prescription is: +1.00 +2.00 x 120

Example 4:

Transpose +3.00 +2.00 x 30

Step 1

Add the sphere and cylinder powers to determine the new sphere power.

(+3.00) + (+2.00) = +5.00

Step 2

Change the sign of the cylinder

-2.00

Step 3

Change the axis by 90 degrees. (if the axis is 90 or less than 90, add 90 degrees to the axis, if the axis is greater than 90 deduct 90 from the axis)

Saturday, July 30, 2011

ASnellen chart is an eye chart used by eye care professionals and others to measure visual acuity. Snellen charts are named after the Dutch ophthalmologist Hermann Snellen who developed the chart during 1862. Vision scientists now use a variation of this chart, designed by Ian Bailey and Jan Lovie .

How to use the eye chart:

The Snellen Eye Chart is read while standing 20 feet from the chart. Be sure the room you are in is well lit but is not in full sunlight.

Test one eye at a time (cover the other eye with your hand or card etc.). The lowest line that you can read correctly is your visual acuity.

At 20 feet (6 meters) you should try to read the letters on the row 6th from the top. If you can read that line ok it means you have visual acuity of 20/40 or better: 1/2 normal.

Standing at 10 feet from the eye chart if the smallest letters you can read were on the 6th row from the top, this would give you an acuity of 10/40: 1/4 normal.

If you are nearsighted, your vision will become clearer the closer you stand to the eye chart.

Visual acuity (VA) is acuteness or clearness of vision. Especially form vision, which is dependent on the sharpness of the retinal focus within the eye, the sensitivity of the nervous elements, and the interpretative faculty of the brain. VA is a quantitative measure of the ability to identify black symbols on a white background at a standardized distance as the size of the symbols is varied. The VA represents the smallest size that can be reliably identified. VA is the most common clinical measurement of visual function.

A visual acuity of 20/20 is frequently described as meaning that a person can see detail from 20 feet away the same as a person with normal eyesight would see from 20 feet. If a person has a visual acuity of 20/40, he is said to see detail from 20 feet away the same as a person with normal eyesight would see it from 40 feet away. Someone with 20/20 visual acuity does not have "perfect" vision, since it is quite possible to see better than 20/20. The maximum acuity of the human eye without visual aids (such as binoculars) is generally thought to be around 20/10 (6/3).

Recent developments in optometry have resulted in corrective lenses conferring upon the wearer a vision of up to 20/10. Some birds, such as hawks, are believed to have an acuity of around 20/2; in this respect, their vision is much better than human eyesight. Many humans have one eye that has superior visual acuity over the other.

The normal height for the letter A is 88 mm, and the viewing distance is 6 meters. To properly view the chart on your monitor:

Measure the height of the letter A in millimeters.

Divide by 88.

Multiply by 6.

The final number is the distance (in meters) that you should stand from the monitor. For information on using the chart to determine your visual acuity.

Friday, July 29, 2011

ZEISS invented the anti-reflective coating almost 75 years ago. We’ve been building on that breakthrough technology ever since, making AR coatings that are clearer, more durable and more convenient to use. With PureCoat™ by ZEISS, they have created our best-performing AR coating ever.

Pure Clarity

Pure Convenience

Pure Durability

Less than 1% luminous reflectance delivers crisper vision and is virtually free from distracting reflections.

PureCoat by ZEISS lets your patients see the world with extraordinary clarity and brilliance. One of the secrets is the unique blue hue of PureCoat by ZEISS, which reduces up to 50% more annoying reflections than other leading AR coatings.

The PureCoat by ZEISS advanced super-hydrophobic and oleophobic coating resists oil and water droplets for easy cleaning throughout the life of the prescription and keeps lenses cleaner, longer..

PureCoat by ZEISS maintains its hydrophobic performance over the lifetime of the prescription. And with up to 50% more scratch resistance than many other leading AR coatings*, PureCoat by ZEISS is extremely durable. When your patients come back for their new prescription, they’ll want PureCoat by ZEISS again.